Process for Producing 3,4-Disubstituted Pyrrolidine Derivative and Production Intermediate Thereof

ABSTRACT

An industrially advantageous process for the production of (3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidine or an enantiomer thereof that is useful as an intermediate for the production of novel antimicrobial agents 10-(3-cyclopropylaminomethyl-4-fluoropyrrolidinyl)pyridobenzoxazine carboxylic acid derivatives. 
     Highly stereoselective asymmetric hydrogenation of 1-protected-4-alkoxycarbonyl-3-oxopyrrolidine, followed by ester hydrolysis, followed by amidation with cyclopropylamine gives crude crystals. The crude crystals are purified by recrystallization to give a novel compound (3R,4S)-1-protected-3-cyclopropylcarbamoyl-4-hydroxypyrrolidine or an enantiomer thereof at high optical purity. The use of these intermediates enables industrial production of high-quality products of (3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidine or an enantiomer thereof. The process is highly simple and can produce the desired products at high purity and stable yields.

TECHNICAL FIELD

The present invention relates to a novel process for the production ofoptically active forms of 3-cyclopropylaminomethyl-4-fluoropyrrolidine,a compound useful as an intermediate for the production of10-(3-cyclopropylaminomethyl-4-fluoropyrrolidinyl)pyridobenzoxazinecarboxylic acid derivatives, antimicrobial agents that are not only safeand potent, but are also effective against drug-resistant bacteria thatcan hardly be killed by conventional antimicrobial agents. The presentinvention also relates to intermediates for the production of3-cyclopropylaminomethyl-4-fluoropyrrolidine.

BACKGROUND ART

The applicant of the present application previously disclosed10-(3-cyclopropylaminomethyl-4-fluoropyrrolidinyl)pyridobenzoxazinecarboxylic acid derivatives as antimicrobial agents that are safe andeffective against drug-resistant bacteria (Patent Document 1). Thispatent document describes a production process of3-cyclopropylaminomethyl-4-fluoropyrrolidine that serves as a usefulintermediate. Nonetheless, the process still had drawbacks that need tobe addressed to make it ideal for mass-production and industrial use.The applicant later disclosed an improved process for synthesizing(3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidine (Patent Document2). The process described in Patent Document 2 uses(3R,4R)-(1-benzyloxycarbonyl-4-hydroxypyrrolidine-3-yl)methano 1 as astarting material. In this process, the primary hydroxyl groups arefirst brominated and the secondary hydroxyl groups are subsequentlyfluorinated. The resulting product is then reacted with acyclopropylamine derivative. Subsequent removal of the benzyloxycarbonylprotecting group gives the target product. Since all of theintermediates produced in this process are oil-like materials, theprocess requires frequent purification by silica gel column to purifythese products. In addition, the introduction of the cyclopropylaminederivative requires an excess amount of cyclopropylamine and heating inan autoclave. Thus, the process is not favorable in terms of workabilityand cost and it has been difficult to implement this process on anindustrial scale. In order to address these problems, there is a need todevelop a production process suitable for practical production of theintermediate.

Patent Document 1: WO03/078439 pamphlet

Patent Document 2: Japanese Patent Application Laid-Open No. 2005-239617DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Accordingly, it is an object of the present invention to provide anindustrially advantageous process for producing high quality products of(3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidine or enantiomersthereof that are useful as intermediates for the production of variouspharmaceutical products.

Means for Solving the Problems

To achieve the above-described objective, the present inventors sought anovel synthetic process of(3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidine or enantiomersthereof and found that(3R,4S)-3-cyclopropylcarbamoyl-4-hydroxypyrrolidine-1-carboxylic acidalkyl ester derivatives, novel intermediates derived from highlystereoselective asymmetric hydrogenation of1-protected-4-alkoxycarbonyl-3-oxopyrrolidine, and their enantiomersexhibit good crystallinity and stability, and that the enantiomeric anddiastereomeric by-products can be effectively separated from thesecompounds. The present inventors then found that high quality, highlypure products of (3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidine orenantiomers thereof can be produced in stable yields in a simple processby carrying out the synthesis via these intermediates. These findingsultimately led to the present invention.

Accordingly, the present invention comprises the following:

(1) A method for producing an optically active3-cyclopropylaminomethyl-4-fluoropyrrolidine represented by thefollowing chemical formula (IX):

or an enantiomer thereof and/or a salt or a hydrate thereof, comprisingthe steps of:

asymmetrically hydrogenating, with a transitional metal catalyst, a1-protected-4-oxo-3-pyrrolidinecarboxylic acid ester derivativerepresented by the following general formula (I):

(wherein R₁ is a protecting group for amino group; and R₂ is a loweralkyl group) to obtain an optically active 4-hydroxy-3-pyrrolidinecarboxylic acid ester derivative of the following general formula (II):

(wherein R₁ and R₂ are as defined above) or an enantiomer thereof;

hydrolyzing the ester group of the compound of the general formula (II)to obtain an optically active 4-hydroxy-3-pyrrolidine carboxylic acidrepresented by the following general formula (III):

(wherein R₁ is as defined above) or an enantiomer thereof;

condensing the compound of the general formula (III) withcyclopropylamine (IV):

to obtain an optically active N-cyclopropyl-4-hydroxy-3-pyrrolidinecarboxylic amide derivative represented by the following general formula(V):

(wherein R₁ is as defined above) or an enantiomer thereof;

reducing the amide group of the compound of the general formula (V) toobtain an optically active 4-hydroxy-3-cyclopropylaminopyrrolidinederivative represented by the following general formula (VI):

(wherein R₁ is as defined above) or an enantiomer thereof and/or a saltor a hydrate thereof;

protecting the amino group of the compound of the general formula (VI)to obtain an optically active 4-hydroxy-3-cyclopropylamino pyrrolidinederivative represented by the following general formula (VII):

(wherein R₁ is as defined above; and R₃ is also an protecting group foramino group and is the same definition as R₁) or an enantiomer thereof;

fluorinating the hydroxyl group at 4th position of the compound of thegeneral formula (VII) to obtain an optically active3-cyclopropylaminomethyl-4-fluoropyrrolidine derivative represented bythe following general formula (VIII):

(wherein R₁ and R₃ are as defined above) or an enantiomer thereof; and

removing the amino-protecting groups R₁ and R₃ of the compound of thegeneral formula (VIII) to obtain the desired compound.

(2) The method for producing optically active3-cyclopropylaminomethyl-4-fluoropyrrolidine or an enantiomer thereofand/or a salt or a hydrate thereof according to (1) above, wherein theamino-protecting groups the R₁ and R₃ represent are each an aralkylgroup, such as a benzyl group and a p-methoxybenzyl group, or analkoxycarbonyl group, such as a methoxycarbonyl group, an ethoxycarbonylgroup, a propyloxycarbonyl group, an isopropyloxycarbonyl group, abutyloxycarbonyl group, an isobutyloxycarbonyl group, atert-butyloxycarbonyl group and an benzyloxycarbonyl group.

(3) An N-cyclopropyl-4-hydroxy-3-pyrrolidine carboxamide derivativerepresented by the following general formula (V):

(wherein R₁ is an amino-protecting group), or an enantiomer thereof.

(4) The N-cyclopropyl-4-hydroxy-3-pyrrolidine carboxamide derivative, oran enantiomer thereof according to (3) above, wherein theamino-protecting group that R₁ represent is an aralkyl group, such as abenzyl group and a p-methoxybenzyl group, or an alkoxycarbonyl group,such as a methoxycarbonyl group, an ethoxycarbonyl group, apropyloxycarbonyl group, an isopropyloxycarbonyl group, abutyloxycarbonyl group, an isobutyloxycarbonyl group, atert-butyloxycarbonyl group and an benzyloxycarbonyl group.

(5) The N-cyclopropyl-4-hydroxy-3-pyrrolidine carboxamide derivative, oran enantiomer thereof according to (3) above, wherein the compound ofthe general formula (V) is(3R,4S)-3-(N-cyclopropyl)carbamoyl-4-hydroxypyrrolidine-1-carboxylicacid benzyl ester,(3S,4R)-3-(N-cyclopropyl)carbamoyl-4-hydroxypyrrolidine-1-carboxylicacid benzyl ester,(3R,4S)-3-(N-cyclopropyl)carbamoyl-4-hydroxypyrrolidine-1-carboxylicacid tert-butyl ester,(3S,4R)-3-(N-cyclopropyl)carbamoyl-4-hydroxypyrrolidine-1-carboxylicacid tert-butyl ester,(3R,4S)-1-benzyl-N-cyclopropyl-4-hydroxy-3-pyrrolidine carboxamide or(3S,4R)-1-benzyl-N-cyclopropyl-4-hydroxy-3-pyrrolidine carboxamide.

EFFECT OF THE INVENTION

According to the present invention, a process has been found that uses(3R,4S)-3-cyclopropylcarbamoyl-4-hydroxypyrrolidine-1-carboxylic acidalkyl ester derivatives, novel intermediates derived from highlystereoselective asymmetric hydrogenation of1-protected-4-alkoxycarbonyl-3-oxopyrrolidine, and their enantiomers toproduce highly pure products of(3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidine or enantiomersthereof, or salts or hydrates thereof in high yields. The presentinvention thus provides an industrial process for the production of(3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidine or enantiomersthereof as well as salts or hydrates thereof that are useful asintermediates for the production of antimicrobial agents.

BEST MODE FOR CARRYING OUT THE INVENTION

The process according to the present invention for producing(3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidine, or enantiomersthereof and salts or hydrates thereof, can be summarized in thefollowing scheme:

(wherein R₁, R₂ and R₃ are as defined above). For ease of understanding,the structure of a compound may be given in this description by aspecific structural formula that shows a particular isomer of thecompound. However, the present invention encompasses all isomers, suchas optical isomers based on asymmetric carbons, stereoisomers andtautomers, and mixtures of such isomers that can arise from thecompound, and is not limited to the exact compounds given by theformula. The invention also encompasses all salts and hydrates of thecompound.

As used herein, the term “C1-4 lower alkyl” that R₂ represents refers toa straight or branched alkyl group having 1 to 4 carbon atoms. Specificexamples include a methyl group, an ethyl group, a n-propyl group, ani-propyl group, a n-butyl group, an i-butyl group, a sec-butyl group anda tert-butyl group.

As used herein, the amino-protecting group that R₁ and R₃ represent maybe any protecting group commonly used as an amino-protecting group.Examples include aralkyl groups, such as a benzyl group and ap-methoxybenzyl group; alkoxycarbonyl groups, such as a methoxycarbonylgroup, an ethoxycarbonyl group, a propyloxycarbonyl group, anisopropyloxycarbonyl group, a butyloxycarbonyl group, anisobutyloxycarbonyl group, a t-butyloxycarbonyl group and abenzyloxycarbonyl group; 1-(alkoxy)alkyl groups, such as a methoxymethylgroup, a methoxyethoxymethyl group, a 1-(ethoxy)ethyl group and amethoxyisopropyl group; and acyl groups, such as an acetyl group, atrifluoroacetyl group, a propionyl group, a butyryl group, a pivaloylgroup, a benzoyl group and a methylbenzoyl group. Of these protectivegroups, aralkyl groups and alkoxycarbonyl groups are preferred becausethey make the intermediates particularly handleable. Of these aralkylgroups and alkoxycarbonyl groups, a benzyl group, a benzyloxycarbonylgroup and a tert-butoxycarbonyl group are particularly preferred.

Each step of the production process of the present invention will now bedescribed in detail.

The starting material used in the process of the present invention is a1-protected-4-oxo-3-pyrrolidine carboxylic acid ester derivativerepresented by the general formula (I). The compound of the generalformula (I) can be prepared according to the technique reported by Choiand Dong Rack et al (Bioorganic & Medicinal Chemistry Letter (2004),14(5), 1273-1277). For example,1-benzyloxycarbonyl-4-ethoxycarbonyl-3-oxopyrrolidine can be produced inthe following manner: a Michael addition is performed using glycineethyl ester hydrochloride and ethyl acrylate. Using reagents such asbenzyl chloroformate, the resulting secondary amino group is protectedwith a benzyloxycarbonyl group. A base such as sodium ethoxide is thenused to cause the protected product to undergo the intramolecularring-forming reaction to form the desired product. Other derivatives canbe produced in a similar manner.

(Step A)

In this step, asymmetric hydrogenation is carried out. The asymmetrichydrogenation reaction can be carried out by using a hydrogen source inthe presence of an optically active catalyst. The optically activecatalyst used is a transitional metal complex having a chiral ligand.The transitional metal may be ruthenium, rhodium, iridium, nickel,palladium and platinum. Ruthenium is preferred due to its availability.While the chiral ligand may be any of the commonly used chiral ligands,those described in the following journal article may preferably be used:CATALYTIC ASYMMETRIC SYNTHESIS Second Edition, 2000, WILEY-VCH, p 2-6.

Examples of such chiral ligands include C2-chiral diphosphines andenantiomers thereof, such as (S,S)-BDPP, (R,R)-BICP, (R)-BIMOP,(S)-BINAP, (S)-TolBINAP, (S)-XylBINAP, (S)-DTBBINAP, (S)-p-MeO-BINAP,(S)-BINAP-SO₃Na, (S)-Cy-BINAP, (S)-BIPHEMP, (S)-MeO-BIPHEP,(S)-p-Tol-MeO-BIPHEP, di-t-Bu-MeO-BIPHEP, (S)—Fr-MeO-BIPHEP, (S)-BICPEP,(S)-BICHEP, (R,R)-BIPNOR, (R,R)-Bis P, (S,S)-t-BuBis P*,(S)-bis-steroidal phosphine, (S)-tetraMe-BITIANP, (S)-Me-BPE,(S)-Et-BPE, (S)-1-BPE, (S,S)-CHIRAPHOS, (R,R)-CDP, (S,S)-DIOP,(S,S)-DIOP-OH, (S,S)-MOD-DIOP, (S,S)-CyDIOP, (S,S)-DIPAMP,(S,S)-Me-DuPHOS, (S,S)-Et-DuPHOS, (S,S)-i-Pr-DuPHOS, (S,S)-FerroPHOS,(S)-HB-BINAP, (S,S)-NORPHOS, (R,S,R,S)-Me-PennPhos, (S)-[2.2]PHANEPHOS,(S,S)-PYRPHOS, (S,S)-RENORPHOS, (S,S,S,S)-RoPHOS, (R,R)-TBPC,(R,R)—(S,S)-TRAP, (R,R)—(S,S)-EtTRAP, (R,R)—(S,S)-i-BuTRAP and(S)-SEGPHOS; non-C2-chiral diphosphines and enantiomers thereof, such as(R)—(S)-BPPFA, (R)—(S)-BPPFOH, (2S,4S)-BPPM, (R)—(S)-BCPM,(R)—(S)-MCCPM, (R)—(S)-m-CH₃POPPM, (R)—(S)-MOD-BCPM, (S)-CAMP,(R)-cy₂-BIPHEMP, (S,R,R,R)-TMO-DEGUPHOS, (R)—(S)-JOSIPHOS,(R)—(S)-XYLIPHOS, (R)—(S)-xyl₂ PF-Pxyl₂, (R)—(S)-MOD-XYLIPHOS,(R)-MOC-BIMOP, (1R,2R)-PPCP, (R)-PROPHOS, (R)-BENZPHOS, (R)-CyCPHOS and(S,S)-SulfBDPP; bisphosphonites and enantiomers thereof, such as(S,S)-BDPCH, (S,S)-BDPCP, (S,R)-BICPO, Ph-β-GLUP, Ph-β-GLUP-OH and(R,R,R)-spirOP; and amidophosphines, aminophosphines and enantiomersthereof, such as (R)-BDPAB, (1S,2R)-DPAMPP, (R)—H₈-BDPAB, (S)-Cp,Cp-IndoNOP, (1S,2S)—Cr(CO)₃-Cp, Cp-IndoNOP, (S)-isoAlaNOP, (S)-Ph,Cp-isoAlaNOP, (S)-Cp, Cp-isoAlaNOP, (S)-Ph, Cp-methyllactamide,(S)-Ph,Ph-oxoProNOP, (S)-Cp, Cp-oxoProNOP, (S)-Cy, Cy-oxoProNOP,(R)-PINDOPHOS, (S,S)-PNNP and (S)-PROLOPHOS. (S)-BINAP is preferablyused due to its availability.

When the transitional metal complexes are used as catalysts, 0.001 to1.0 mols of the catalyst are used for 1 mol of the reaction substrate.

The hydrogen source may be hydrogen and formic acid/triethylaminesystem, formic acid/α-phenethylamine system, formic acid/triphenylaminesystem or 2-propanol.

The reaction generally requires a solvent. Examples of the solventinclude water; organic acids, such as formic acid and acetic acid;esters, such as ethyl acetate and butyl acetate; aromatic compounds,such as benzene, toluene and xylene; hydrocarbons, such as hexane,heptane and cyclohexane; alcohols, such as methanol, ethanol, t-butylalcohol, ethylene glycol and diethylene glycol; ethers, such as dioxane,tetrahydrofuran, dimethoxyethane and diglyme; halogenated hydrocarbons,such as dichloromethane, chloroform, carbon tetrachloride and1,2-dichloroethane; and mixtures thereof. Of these, alcohols such asethanol and halogenated hydrocarbons such as dichloromethane arepreferred.

The reaction is typically carried out at a temperature in the range of−20° C. to 200° C., and preferably in the range of 25° C. to 100° C.

The reaction pressure is typically in the range of atmospheric pressureto 20 MPa.

(Step B)

In this step, the ester group is hydrolyzed. The ester hydrolysis can beperformed using conditions commonly used for this purpose. For example,the reaction can be carried out in the presence of an alkali reagent,such as sodium hydroxide, or in the presence of an inorganic acid, suchas hydrochloric acid, or an organic acid, such as trifluoro acetic acid,and in a solvent, such as an alcohol (such as methanol, ethanol andpropanol), tetrahydrofuran, t-butyl methyl ether and cyclopentyl methylether. While the reaction may be carried out at any temperature in therange of −20° C. to the boiling point of the solvent used, it ispreferably carried out in the range of 0° C. to room temperature.

(Step C)

In this step, the pyrrolidine carboxylic acid derivative (III) isamidated with cyclopropylamine. The amidation reaction can be performedby using commonly used condensation conditions.

When a condensation agent is used, it may be any condensation agent thatcan form an amide linkage between a carboxylic acid and an amine. Thecondensation agent is preferably1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride,dicyclohexylcarbodiimide, diethyl phosphorocyanidate, carbodiimidazole,diphenylphosphoryl azide or 1-hydroxybenzotriazole. Of these,1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and1-hydroxybenzotriazole are particularly preferred. The base used may beany base that does not interfere with the reaction. Examples includeorganic amines such as triethylamine, trimethylamine, pyridine,dimethylaniline, N-methylmorpholine and 4-dimethylaminopyridine. Ofthese, triethylamine is particularly preferred. The reaction generallyrequires a solvent, examples including esters, such as ethyl acetate andbutyl acetate; aromatic compounds, such as benzene, toluene and xylene;hydrocarbons, such as hexane, heptane and cyclohexane; ethers, such asdioxane, tetrahydrofuran, dimethoxyethane and diglyme; halogenatedhydrocarbons, such as dichloromethane, chloroform, carbon tetrachlorideand 1,2-dichloroethane; nitriles, such as acetonitrile; and mixturesthereof. Of these, tetrahydrofuran, ethyl acetate and acetonitrile areparticularly preferred in the reaction.

While the reaction may be carried out at any temperature in the range of−20° C. to the boiling point of the solvent used, it is preferablycarried out at a temperature in the range of 0° C. to the boiling pointof the solvent used.

Alternatively, the compound (III) may be reacted with a reactivederivative to form the compound (IV). Examples of such reactivederivatives include acid halides, such as acid chlorides and acidbromides; active esters, such as N-hydroxybenzotriazole andN-hydroxysuccinimide; mixed anhydrides with monoethyl carbonate andmonophenyl carbonate; and anhydrides of the compound (III). Activeesters using N-hydroxybenzotriazole are particularly preferred. Thereaction is typically carried out either in the absence of solvents orin the presence of an inert solvent. When necessary, a base is added tothe reaction system. The base may be any base that does not interferewith the reaction. Examples of the base include organic amines, such astriethylamine, trimethylamine, pyridine, dimethylaniline,N-methylmorpholine and 4-dimethylaminopyridine. Of these, triethylamineis preferred. Examples of the solvent include esters, such as ethylacetate and butyl acetate; aromatic compounds, such as benzene, tolueneand xylene; hydrocarbons, such as hexane, heptane and cyclohexane;ethers, such as dioxane, tetrahydrofuran, dimethoxyethane and diglyme;halogenated hydrocarbons, such as dichloromethane, chloroform, carbontetrachloride and 1,2-dichloroethane; nitriles, such as acetonitrile;and mixtures thereof. Of these, tetrahydrofuran, ethyl acetate andacetonitrile are particularly preferred in the reaction. While thereaction may be carried out at any temperature in the range of −20° C.to the boiling point of the solvent used, it is preferably carried outat a temperature in the range of 0° C. to the boiling point of thesolvent used.

(Step D)

In this step, the amide group is reduced. Examples of the reducing agentused include BH₃-THF, BH₃—SMe₂, LiAlH(OMe)₃, LiAlH₄, AlH₃, LiBEt₃H,(i-Bu)₂AlH, NaAlEt₂H₂, NaBH₄—ZnCl₂, NaBH₄—BF₃OEt₂, NaBH₄-TMSCl,NaBH₄-LiCl, NaBH₄—AlCl₃ and NaBH₄—CoCl₂. Of these, BH₃-THF is preferred.

The reaction generally requires a solvent. Examples of the solventinclude ethers, such as tetrahydrofuran, cyclopentyl methyl ether,dioxane, dimethoxyethane and diglyme; aromatic compounds, such asbenzene, toluene and xylene; hydrocarbons, such as hexane, heptane andcyclohexane; alcohols, such as methanol, ethanol, t-butyl alcohol,ethylene glycol and diethylene glycol; and mixtures thereof.

While the reaction may be carried out at any temperature in the range of−70° C. to the boiling point of the solvent used, it is preferablycarried out at a temperature in the range of −10° C. to the boilingpoint of the solvent used. When BH₃-THF is used as the reducing agent,typically 1.0 to 20 mols, preferably 1.0 to 3.0 mols of the reducingagent are used for 1 mol of the compound (IV). The reaction generallyrequires a solvent, examples including ethers, such as tetrahydrofuran,cyclopentyl methyl ether, dioxane, dimethoxyethane and diglyme; aromaticcompounds, such as benzene, toluene and xylene; hydrocarbons, such ashexane, heptane and cyclohexane; and mixtures thereof. Of thesesolvents, ethers are preferred with tetrahydrofuran being particularlypreferred. While the reaction may be carried out at any temperature inthe range of −70° C. to the boiling point of the solvent used, it ispreferably carried out at a temperature in the range of −10° C. to theboiling point of the solvent used.

(Step E)

In this step, the protecting group R₃ is introduced into the aminogroup. The amino-protecting group that R₃ represents may be anyprotecting group commonly used as an amino-protecting group. Examplesinclude aralkyl groups, such as a benzyl group and a p-methoxybenzylgroup; alkoxycarbonyl groups, such as a methoxycarbonyl group, anethoxycarbonyl group, a propyloxycarbonyl group, an isopropyloxycarbonylgroup, a butyloxycarbonyl group, an isobutyloxycarbonyl group, at-butyloxycarbonyl group and a benzyloxycarbonyl group; 1-(alkoxy)alkylgroups, such as a methoxymethyl group, a methoxyethoxymethyl group, a1-(ethoxy)ethyl group and a methoxyisopropyl group; and acyl groups,such as an acetyl group, a trifluoroacetyl group, a propionyl group, abutyryl group, a pivaloyl group, a benzoyl group and a methylbenzoylgroup. Of these protecting groups, aralkyl groups and alkoxycarbonylgroups are preferred because they make the intermediates particularlyhandleable. Of these aralkyl groups and alkoxycarbonyl groups, a benzylgroup, a benzyloxycarbonyl group and a tert-butoxycarbonyl group areparticularly preferred. These protecting groups can be introduced byusing any of the described techniques (See, for example, Green, T. W.;Wuts, P. G. M. “Protective Groups in Organic Synthesis,” 2nd Ed., WileyInterscience Publication, John-Wiley & Sons, New York, 1991, p 309-p348).

For example, when the amino-protecting group is a benzyl group, anaralkyl-containing compound such as benzyl bromide and benzyl chloridemay be used in a proper solvent in the presence of a base. When theamino-protecting group is an alkoxycarbonyl group such ast-butoxycarbonyl group and benzyloxycarbonyl group, a chlorocarbonateester such as benzyl chlorocarbonate, or a dicarbonate diester such ast-butoxycarbonyl dicarbonate may be used. A base is used when necessary.Examples of the base include inorganic bases, such as lithium hydroxide,sodium hydroxide, potassium hydroxide, sodium carbonate, potassiumcarbonate, cesium carbonate, sodium bicarbonate and potassiumbicarbonate; organic bases, such as triethylamine,diisopropylethylamine, 4-methylmorpholine, 4-ethylmorpholine, pyridine,1-methylimidazole, 1,2-dimethylimidazole,1,5-diazabicyclo[4.3.0]-5-nonene and 1,5-diazabicyclo[5.4.0]-5-undecene;and alkali metal alkoxides, such as lithium methoxide, lithium ethoxide,sodium methoxide, sodium ethoxide, sodium t-butoxide, potassiummethoxide, potassium ethoxide and potassium t-butoxide.

The reaction generally requires a solvent. Examples of the solventinclude ethers, such as tetrahydrofuran, cyclopentylmethyl ether,dioxane, dimethoxyethane and diglyme; aromatic compounds, such asbenzene, toluene and xylene; hydrocarbons, such as hexane, heptane andcyclohexane; alcohols, such as methanol, ethanol, t-butyl alcohol,ethylene glycol and diethylene glycol; water; and mixtures thereof.

While the reaction may be carried out at any temperature in the range of−70° C. to the boiling point of the solvent used, it is preferablycarried out in the range of −10° C. to the boiling point of the solventused.

(Step F)

In this step, the hydroxyl group is converted into the fluorine group.The fluorination reaction can be carried out by using commonly usedconditions. For example, a perfluoroalkylsulfonyl fluoride, such asperfluoro-1-butanesulfonyl fluoride or 1-octanesulfonyl fluoride or adialkylaminosulfur trifluoride such as diethylaminosulfur trifluoride,morpholinosulfur trifluoride or bis(2-methoxyethyl)aminosulfurtrifluoride is used for the purpose in a proper solvent and whennecessary, in the presence of a base.

Perfluoroalkylsulfonyl fluorides are generally used in conjunction witha base, which may be any base that does not interfere with the reaction.Examples of the base include organic amines, such as1,8-diazabicyclo[5.4.0]undeca-7-ene, triethylamine, trimethylamine,pyridine, dimethylaniline and N-methylmorpholine. Of these bases,1,8-diazabicyclo[5.4.0]undeca-7-ene is particularly preferred.

The reaction generally requires a solvent. Examples of the solventinclude esters, such as ethyl acetate and butyl acetate; aromaticcompounds, such as benzene, toluene and xylene; hydrocarbons, such ashexane, heptane and cyclohexane; ethers, such as dioxane,tetrahydrofuran, dimethoxyethane and diglyme; halogenated hydrocarbons,such as dichloromethane, chloroform, carbon tetrachloride and1,2-dichloroethane; nitriles, such as acetonitrile; and mixturesthereof. Of these solvents, toluene is particularly preferred. While thereaction may be carried out at any temperature in the range of −70° C.to the boiling point of the solvent used, it is preferably carried outin the range of −10° C. to the boiling point of the solvent used.

When dialkylaminosulfur trifluorides are used, a solvent is generallyrequired. Examples of the solvent include esters, such as ethyl acetateand butyl acetate; aromatic compounds, such as benzene, toluene andxylene; hydrocarbons, such as hexane, heptane and cyclohexane; ethers,such as dioxane, tetrahydrofuran, dimethoxyethane and diglyme;halogenated hydrocarbons, such as dichloromethane, chloroform, carbontetrachloride and 1,2-dichloroethane; nitriles, such as acetonitrile;and mixtures thereof. Of these solvents, dichloromethane andacetonitrile are particularly preferred. While the reaction may becarried out at any temperature in the range of −70° C. to the boilingpoint of the solvent used, it is preferably carried out in the range of−10° C. to the boiling point of the solvent used.

(Step G)

In this step, the amino-protecting group is removed. The introductionand the removal of these protecting groups can be performed by using anyof the described techniques (Green, T. W.; Wuts, P. G. M. “ProtectiveGroups in Organic Synthesis,” 2nd Ed., Wiley Interscience Publication,John-Wiley & Sons, New York, 1991, p 309-p 348). For example, when R₁and R₃ of the compound of the general formula (VII) are each anaralkyloxy group, such as benzyloxycarbonyl group, or an aralkyl group,such as benzyl group and p-methoxybenzyl group, the protecting groupscan be removed at once by carrying out catalytic hydrogenation in thepresence of a catalyst. When R₁ and R₃ of the compound (VII) are each at-butoxycarbonyl group, the protecting groups can be removed at once bythe use of an organic acid or an inorganic acid.

When R₁ and R₃ of the compound (VII) require different conditions forremoval, the above-described techniques may be combined. Aralkyl groupssuch as benzyloxycarbonyl group and benzyl group can be removed byperforming catalytic hydrogenation in the presence of a hydrogen source.Examples of the catalyst that can be used include palladium catalysts,such as palladium/carbon, palladium/alumina, palladium black andpalladium oxide. Of these, palladium/carbon is particularly preferred.

The hydrogen source may be hydrogen and formic acid/triethylaminesystem, formic acid/α-phenethylamine system, formic acid/triphenylaminesystem or 2-propanol. Of these, hydrogen is particularly preferred. Thereaction pressure is typically in the range of atmospheric pressure to10 MPa, and preferably in the range of atmospheric pressure to 1 MPa.

The reaction generally requires a solvent. Examples of the solventinclude alcohols, such as methanol, ethanol, t-butyl alcohol, ethyleneglycol and diethylene glycol; water; ethers, such as tetrahydrofuran,cyclopentyl methyl ether, dioxane, dimethoxyethane and diglyme; aromaticcompounds, such as benzene, toluene and xylene; hydrocarbons, such ashexane, heptane and cyclohexane; and mixtures thereof.

While the reaction may be carried out at any temperature in the range of0° C. to the boiling point of the solvent used, it is preferably carriedout in the range of room temperature to the boiling point of the solventused. To accelerate the reaction, an acid, such as sulfuric acid,hydrochloric acid, phosphoric acid and perchloric acid, or a base, suchas ammonia, pyridine, triethylamine, sodium hydroxide and potassiumhydroxide, may be added to the reaction system.

Any solvent that is commonly used in organic synthesis and does notinterfere with the reaction may be used in the present invention.Examples of such solvents include lower alcohols, such as methanol,ethanol, propanol and butanol; polyalcohols, such as ethylene glycol andglycerol; ketones, such as acetone, methyl ethyl ketone and cyclohexane;ethers, such as diethyl ether, diisopropyl ether, tetrahydrofuran,dioxane, 2-methoxyethanol, 1,2-dimethoxyethane and cyclopentyl methylether; nitriles, such as acetonitrile and propionitrile; esters, such asmethyl acetate, ethyl acetate, isopropyl acetate and butyl acetate;halogenated hydrocarbons, such as dichloromethane, chloroform, carbontetrachloride and 1,2-dichloroethane; aromatic compounds, such asbenzene, toluene, xylene, monochlorobenzene, nitrobenzene, pyridine,quinoline, collidine and phenol; hydrocarbons, such as pentane,cyclohexane, hexane, heptane, petroleum ether and petroleum benzene;amines, such as ethanolamine, diethylamine, triethylamine, pyrrolidine,piperazine, morpholine, aniline, dimethylaniline, benzylamine andtoluidine; amides, such as formamide, N-methylpyrrolidone andN,N-dimethylformamide; sulfoxides, such as dimethyl sulfoxide andsulfolane; hexamethylphosphoric triamide; water; and other commonly usedsolvents and mixtures of two or more of these solvents, which maycontain each solvent in any proportion. When desired, it may be purifiedand isolated upon completion of the reaction by using common separationtechniques (such as extraction, recrystallization and chromatography).

The compounds of the present invention can be produced by the processesdescribed in examples hereinbelow. However, these examples are intendedto be only illustrative and the compounds of the present invention areby no means limited to those presented in the examples.

EXAMPLES Reference Example 1 Synthesis of ethyl3-(ethoxycarbonylmethylamino)propionate

150 g of glycine ethyl ester hydrochloride (1.07 mol) was mixed with1.200 L of ethanol. To this mixture, 110 mL of ethyl acrylate (1.02 mol)was added at an internal temperature of 2 to 25° C. 150 mL oftriethylamine (1.08 mol) was then added dropwise at an internaltemperature of 20 to 21° C. over 5 minutes. Subsequently, the mixturewas stirred at an internal temperature of 23 to 27° C. for 8.5 hours andwas allowed to stand overnight. The insoluble material was separated byfiltration and the filtrate was evaporated under reduced pressure. 300mL of ethyl acetate was added to the resulting residue and the insolublematerial was separated by filtration and washed with 50 mL of ethylacetate. The filtrate and the wash were combined and concentrated underreduced pressure. The resulting residue was distilled under reducedpressure (533 Pa, 130° C.) to give 138 g of the title compound as acolorless oil (67% yield).

¹H-NMR (CDCl₃, 400 MHz) δ: 1.27 (3H, t, J=7.1 Hz), 1.28 (3H, t, J=7.3Hz), 2.51 (2H, t, J=6.6 Hz), 2.90 (2H, t, J=6.6 Hz), 3.42 (2H, s), 4.15(2H, q, J=7.1 Hz), 4.19 (2H, q, J=7.1 Hz). FAB-MS (positive): 204 [M+H]⁺

Reference Example 2 Synthesis of ethyl3-benzyloxycarbonyl-3-(ethoxycarbonylmethylamino)propionate

0.95 kg of ethyl 3-(ethoxycarbonylmethylamino)propionate (4.68 mol) wasdissolved in 2.85 L of ethanol and 2.85 L of water. To this solution,0.41 kg of sodium bicarbonate (4.91 mol) was added under stirring.Subsequently, 0.84 kg of benzylchloroformate (4.91 mol) was addeddropwise at an internal temperature of 28 to 35° C. and the mixture wasstirred at an internal temperature of 28 to 35° C. for 2 hours. Ethanolwas evaporated under reduced pressure and 9.51 L of ethyl acetate wasadded. The mixture was then stirred for 5 minutes. The mixture wasallowed to stand and the organic layer (top layer) was collected. Tothis layer, 4.8 L of water was added and the mixture was stirred for 5minutes. The mixture was allowed to stand again and the organic layer(top layer) was collected. To this layer, 4.8 L of 28% brine was addedand the mixture was stirred for 5 minutes. The mixture was allowed tostand again and the organic layer (top layer) was collected. To thislayer, 0.57 kg of anhydrous sodium sulfate was added and the mixture wasstirred for 1 hour. The solid was separated by filtration and washedwith 0.95 L of ethyl acetate. The filtrate and the wash were combinedand concentrated under reduced pressure. The resulting product was driedunder reduced pressure at an external temperature of 50° C. for 30minutes. This gave 1.64 kg of a crude product of the title compound as acolorless oil. This product was used in the subsequent step withoutfurther purification.

ESI-MS (positive): m/z 338 [M+H]⁺

Reference Example 3 Synthesis of 1-benzyl 3-ethyl4-oxopyrrolidine-1,3-dicarboxylate

0.35 kg of sodium ethoxide (5.15 mol) was suspended in 9.47 L oftetrahydrofuran. While this suspension was stirred, 3.16 L of atetrahydrofuran solution containing 1.64 kg of the crude product ofethyl 3-benzyloxycarbonyl-3-(ethoxycarbonylmethylamino)propionate(equivalent to 4.68 mol) was added dropwise at an internal temperatureof 25 to 32° C. The mixture was then stirred at an internal temperatureof 25 to 32° C. for 2 hours. While the reaction mixture was stirred,5.15 L of 1 mol/L hydrochloric acid (pH 4.78) was added at an internaltemperature of 27 to 28° C. and the mixture was stirred for 10 minutes(pH changed from 4.78 to 4.76). Subsequently, tetrahydrofuran (approx.12 L) was evaporated under reduced pressure. To the resulting residue,7.89 L of ethyl acetate was added and the mixture was stirred for 5minutes. The reaction mixture was then allowed to stand and the organiclayer (top layer) was collected. To this layer, 3.95 L of water wasadded and the mixture was stirred for 5 minutes. The mixture was allowedto stand again and the organic layer (top layer) was collected. To thislayer, 3.95 L of 28% brine was added and the mixture was stirred for 5minutes. The mixture was allowed to stand again and the organic layer(top layer) was collected. To this layer, 0.39 kg of anhydrous sodiumsulfate was added and the mixture was stirred for 1 hour. The resultingsolid was separated by filtration and washed with 1.58 L of ethylacetate. The filtrate and the wash were combined and concentrated underreduced pressure. This product was then dried under reduced pressure atan external temperature of 40° C. for 30 minutes. The resulting palebrown oil (1.52 kg) was dissolved in 9.47 L of diisopropyl ether and thesolution was stirred at an internal temperature of 25° C. Once theformation of crystals was observed (internal temperature of 25° C.), thesolution was further stirred for 15 minutes at an internal temperatureof 25 to 28° C. Subsequently, the solution was cooled in an ice bathunder stirring and was kept stirred for 30 minutes at an internaltemperature of 10° C. or below. The crystals were then collected byfiltration at an internal temperature of 7° C. and washed with achilled, 4:1 mixture of diisopropylether/hexane (3.95 L, internaltemperature of 3° C.). The washed crystals were drained for 15 minutesand air-dried overnight. Subsequently, the product was dried underreduced pressure at 40° C. for 9 hours. This gave 1.03 kg of the titlecompound as a faintly yellowish white powder (75% yield in the twosteps).

Melting Point: 56.6-59.7° C.

EI-MS: m/z 91 (base peak), 291 (M)⁺

Example 1 Synthesis of 1-benzyl 3-ethyl(3S,4R)-4-hydroxypyrrolidine-1,3-dicarboxylate

90 mL of dehydrated N,N-dimethylformamide was added to 2.58 g of benzeneruthenium (II) chloride dimer (5.15 mmol) and 6.73 g of(S)-(−)-2,2,′-bis(diphenylphosphino)-1,1-binaphthyl (S-BINAP) (10.8mmol). The mixture was stirred for 10 minutes in an oil bath at anexternal temperature of 97 to 102° C. in an argon atmosphere.Subsequently, the mixture was stood to be cooled at room temperature.Volatile materials were evaporated under reduced pressure in an oil bathat an external temperature of 50 to 60° C. to give a catalyst. 300 g of1-benzyl 3-ethyl 4-oxopyrrolidine-1,3-dicarboxylate (1.03 mol) and 500mL of dehydrated dichloromethane were placed in an autoclave and theruthenium catalyst dissolved in 850 mL of dehydrated dichloromethane wasadded. The mixture was stirred for 6 hours under a hydrogen pressure of5 MPa at an external temperature of 50 to 62° C. Hydrogen was releasedand the reaction mixture was concentrated under reduced pressure. Thisgave 320 g of the title compound as a green oil. This product was usedin the subsequent step without further purification.

¹H-NMR (CDCl₃, 400 MHz) δ: 1.27 (3H, t, J=7.1 Hz), 2.31-2.40 (1H, m),2.96-3.10 (1H, m), 3.36 (1H, ddd, J=12.0, 5.4, 2.7 Hz), 3.66 (1H, dd,J-11.2, 7.1 Hz), 3.76-3.87 (2H, m), 4.19 (2H, q, J=7.1 Hz), 4.56-4.59(1H, m), 5.14 (2H, s), 7.29-7.37 (5H, m).

CI-MS (positive): m/z 294 [M+H]⁺

Example 2 Synthesis of(3S,4R)-1-benzyloxycarbonyl-4-hydroxypyrrolidine-3-carboxylic acid

639 g of 1-benzyl 3-ethyl (3S,4R)-4-hydroxypyrrolidine-1,3-dicarboxylate(equivalent to 1.03 mol) was dissolved in 3.02 L of ethanol and 3.02 Lof water was added to the solution. While the mixture was stirred andcooled in an ice bath, a sodium hydroxide solution (formed by dissolving124 g of sodium hydroxide (3.09 mol) in 3.02 L of water) was addeddropwise at an internal temperature of 6.0 to 9.8° C. and the mixturewas subsequently stirred at an internal temperature of 6 to 10° C. for 1hour. This was followed by addition of 60.4 g of active carbon. Themixture was then taken out of the ice bath and stirred at roomtemperature for 30 minutes. The insoluble material was separated byfiltration and washed with 1.21 L of water. The filtrate and the washwere combined and concentrated under reduced pressure. To the resultingresidue, 3.02 L of diisopropyl ether was added and the mixture wasstirred for 5 minutes. Subsequently, the mixture was allowed to standardthe aqueous layer (bottom layer) was collected. To the aqueous layer,3.02 L of diisopropyl ether was added and the mixture was stirred for 5minutes. The mixture was allowed to stand again and the aqueous layer(bottom layer) was collected. While the aqueous layer was stirred, 0.54L of 6 mol/L hydrochloric acid was added dropwise (pH changed from 12.8to 1.5). To the resulting mixture, 4.83 L of ethyl acetate and 1.21 kgof sodium chloride were added and the mixture was stirred for 5 minutes.The mixture was then allowed to stand and the organic layer (top layer)was collected. To the organic layer, 3.02 L of 28% brine was added andthe mixture was stirred for 5 minutes. The mixture was then allowed tostand again and the organic layer (top layer) was collected. To theorganic layer, 302 g of anhydrous sodium sulfate was added and themixture was stirred for 1 hour. The resulting solid was separated byfiltration and washed with 0.90 L of ethyl acetate. The filtrate and thewash were combined and concentrated under reduced pressure to give 620 gof a crude product of the title compound as a pale brown solid. Thisproduct was used in the subsequent step without further purification.

¹H-NMR (CDCl₃, 400 MHz) δ: 3.01-3.10 (1H, m), 3.34-3.41 (1H, m),3.54-3.86 (3H, m), 4.60 (1H, q, J=5.5 Hz), 5.13 (2H, s), 7.30-7.36 (5H,m).

CI-MS (positive): m/z 266 [M+H]⁺

Example 3 Synthesis of benzyl(3S,4R)-3-(N-cyclopropyl)carbamoyl-4-hydroxypyrrolidine-1-carboxylate

5.46 L of tetrahydrofuran was added to 619 g of(3S,4R)-1-benzyloxycarbonyl-4-hydroxypyrrolidine-3-carboxylic acid(equivalent to 2.06 mol) to dissolve the compound. While this solutionwas stirred, 379 g of 1-hydroxybenzotriazole hydrate (2.47 mol), 294 gof cyclopropylamine (5.15 mol) and 474 g of1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (2.47 mol)were successively added. The resulting mixture was stirred at aninternal temperature of 26 to 40° C. for 5 hours. The reaction mixturewas then concentrated under reduced pressure. To the resulting residue,2.73 L of ethyl acetate and 5.46 L of 1 mol/L hydrochloric acid wereadded and the mixture was stirred for 30 minutes. The precipitated solidwas separated by filtration and washed with 0.55 L of ethyl acetate. Thefiltrate and the wash were combined, followed by addition of 2.18 L ofethyl acetate and 546 g of sodium chloride and stirring for 5 minutes.Subsequently, the mixture was allowed to stand and the organic layer(top layer) was collected. To the organic layer, 2.73 L of 10% sodiumbicarbonate was added and the mixture was stirred for 5 minutes. Themixture was allowed to stand again and the organic layer (top layer) wascollected. To the organic layer, 2.73 L of 28% brine was added and themixture was stirred for 5 minutes. The mixture was then allowed to standagain and the organic layer (top layer) was collected. To the organiclayer, 0.82 kg of anhydrous sodium sulfate was added and the mixture wasstirred for 1 hour. The resulting solid was separated by filtration andwashed with 1.09 L of ethyl acetate. The filtrate and the wash werecombined and concentrated under reduced pressure to give a faint yellowsolid (706 g). To this solid, 3.28 L of diisopropyl ether was added andthe mixture was stirred for 30 minutes. The solid was collected byfiltration and washed with 0.82 L of diisopropyl ether. The washedproduct was drained for 1 hour and dried by air-blowing at 50° C. for 16hours. This gave faintly yellow white powder crystals (534 g). To 534 gof the crystals, 6.40 L of ethyl acetate was added and the mixture washeated under stirring until the crystals dissolved (internal temperatureof 70° C.) The mixture was allowed to cool under stirring. Following theformation of crystals (internal temperature of 57° C.), the mixture waskept stirred until its internal temperature was 50° C. Subsequently, themixture was cooled in a water bath while being stirred and the crystalswere collected by filtration at an internal temperature of 25° C. andwashed with 1.07 L of diisopropyl ether. The product was drained for 1hour and dried by air-blowing at 60° C. for 19 hours to give 375 g ofthe title compound as fluffy white crystals (60% yield in the 3 steps).

Melting point: 134.5-135.2° C.

¹H-NMR (CDCl₃, 400 MHz) δ: 0.44 (2H, m), 0.71-0.81 (2H, m), 2.66-2.79(2H, m), 3.25 (1H, dd, J=10.9, 6.9 Hz), 3.37-3.62 (2H, m), 3.70-3.86(2H, m), 4.38-4.51 (1H, m), 5.12 (2H, s), 6.29 (1H, br s), 7.28-7.38(5H, m).

CI-MS (positive): m/z 305 [M+H]⁺

[α]_(D) ²⁴ 25.0 (c=0.30, methanol)

Optical purity: 99.9% ee

(HPLC Conditions)

Column ═CHIRAL CELL AD-RH (4.69×150 mm), Daicel; precolumn ═INERTSILODS-3 (4.0φ×10 mm), GL Sciences; detection wavelength=210 mm; flowrate=1.0 mL/min; mobile phase=diluted phosphoric acid (1 to 1000 fold);acetonitrile=75:25; RT=14.05 min.

Example 4 Synthesis of Benzyl(3S,4R)-3-cyclopropylaminomethyl-4-hydroxypyrrolidine-1-carboxylate

364 g of benzyl(3S,4R)-3-(N-cyclopropyl)carbamoyl-4-hydroxypyrrolidine-1-carboxylate(1.20 mol) was suspended in 1.46 L of dehydrated tetrahydrofuran. Whilethis suspension was stirred, 3.07 L of a 1.17 M tetrahydrofuran solutionof borane-tetrahydrofuran complex in (3.59 mol) was added dropwise at aninternal temperature of 20 to 43° C. The mixture was stirred at aninternal temperature of 41 to 46° C. for 8 hours. Subsequently, themixture was allowed to cool under stirring and then cooled in an icebath while kept stirred. 364 mL of water was then added dropwise at aninternal temperature of 15 to 25° C. Subsequently, 726 g oftriethylamine was added dropwise at an internal temperature of 16 to 18°C. The mixture was then heated and stirred for 14 hours under reflux.Subsequently, the reaction mixture was allowed to cool under stirringand concentrated under reduced pressure. To the resulting residue, 1.09L of water was added to dissolve the solid and the solution wasextracted with 2.55 L of ethyl acetate. The organic layer was washedwith 1.82 L of water and extracted with 1.50 L of 2 mol/L hydrochloricacid. A 2 mol/L sodium hydroxide solution (1.67 L) was then added to theaqueous layer under stirring until pH 12. The mixture was extracted with2.55 L of ethyl acetate and the organic layer was washed with 1.82 L of28% brine. To this layer, 255 g of anhydrous sodium sulfate was addedand the mixture was stirred for 1 hour. The resulting solid wasseparated by filtration and washed with 0.55 L of ethyl acetate. Thefiltrate and the wash were combined and concentrated under reducedpressure to give 345 g of a crude product of the title compound as afaint yellow oil. This product was used in the subsequent step withoutfurther purification.

¹H-NMR (CDCl₃, 400 MHz) δ: 0.26-0.53 (4H, m), 2.06-2.21 (2H, m), 2.66(1H, t, J=11.3 Hz), 2.95-3.09 (2H, m), 3.20 (1H, ddd, J=31.0, 15.5, 7.8Hz), 3.65 (1H, ddd, J=16.2, 8.3, 5.3 Hz), 3.75-3.81 (1H, m), 4.10 (1H,q, J=7.3 Hz), 5.09-5.15 (2H, m), 7.28-7.43 (5H, m).

CI-MS (positive): m/z 291 [M+H]⁺

Example 5 Synthesis of Benzyl(3S,4R)-3-cyclopropylaminomethyl-4-hydroxypyrrolidine-1-carboxylatehydrochloride

4.86 L of ethyl acetate was added to 345 g of benzyl(3S,4R)-3-cyclopropylaminomethyl-4-hydroxypyrrolidine-1-carboxylate(1.20 mol) to dissolve the compound. While this solution was stirred,1.04 L of a 10%% hydrogen chloride methanol solution was added at aninternal temperature of 21° C. Following the formation of crystals(internal temperature of 20° C.), the mixture was kept stirred for 15minutes. Subsequently, 9.72 L of diisopropyl ether was added slowly andthe mixture was further stirred for 30 minutes. The resulting crystalswere collected by filtration, washed with 0.52 L of ethyl acetate, anddrained for 30 minutes. The product was then dried by air-blowing at 60°C. for 4 hours to give 350 g of the title compound as white powdercrystals (90% yield in the 2 steps).

Melting point: 153.6-155.4° C.

¹H-NMR (DMSO-d₆, 400 MHz) δ: 0.68-0.94 (4H, m), 2.29-2.45 (1H, m),2.63-2.77 (1H, m), 2.91-3.05 (1H, m), 3.07-3.26 (3H, m), 3.52-3.66 (2H,m), 4.06 (1H, br s), 5.07 (2H, dd, J=14.2, 12.0 Hz), 5.47 (1H, br s),7.29-7.40 (5H, m), 8.57 (2H, brs).

CI-MS (positive): m/z 291 [M+H]⁺

[α]_(D) ²⁴ 36.7 (c=0.30, methanol)

Example 6 Synthesis of benzyl(3S,4R)-3-(N-benzyl-N-cyclopropyl)aminomethyl-4-hydroxypyrrolidine-1-carboxylate

942 mL of ethanol and 942 mL of purified water were added to 314 g ofbenzyl(3S,4R)-3-cyclopropylaminomethyl-4-hydroxypyrrolidine-1-carboxylatehydrochloride(0.96 mol) to dissolve the compound. While this solution was stirred,178 g of sodium bicarbonate (2.11 mol) was added at an internaltemperature of 27 to 29° C. 197 g of benzyl bromide (1.15 mol) was thenadded dropwise at an internal temperature of 25 to 27° C. and themixture was stirred for 2 hours at an internal temperature of to 40 to44° C. The ethanol component of the reaction mixture was concentratedunder reduced pressure and the resulting residue was extracted with 1.57L of ethyl acetate. The organic layer was washed successively with 628mL of 2% brine and 942 mL of 28% brine and dried over anhydrous sodiumsulfate. The resulting solid was separated by filtration and washed with471 mL of ethyl acetate. The filtrate and the wash were combined andconcentrated under reduced pressure to give 392 g of a crude product ofthe title compound as a faint yellow oil. This product was used in thesubsequent step without further purification.

¹H-NMR (CDCl₃, 400 MHz) δ: 0.34-0.56 (4H, m), 1.77-1.84 (1H, m),2.33-2.43 (1H, m), 2.54-2.72 (2H, m), 2.90-2.95 (1H, m), 3.18 (1H, ddd,J=16.4, 9.5, 5.6 Hz), 3.53-3.67 (3H, m), 3.85-3.90 (2H, m), 5.11 (2H,s), 7.24-7.40 (10H, m).

ESI-MS (positive): m/z 381 [M+H]⁺

Example 7 Synthesis of benzyl

(3S,4S)-3-(N-benzyl-N-cyclopropyl)aminomethyl-4-fluoropyrrolidine-1-carboxylate

3.66 L of toluene was added to 391 g of benzyl(3S,4R)-3-(N-benzyl-N-cyclopropyl)aminomethyl-4-hydroxypyrrolidine-1-carboxylate(equivalent to 0.96 mol) to dissolve the compound. To this solution,1,8-diazabicyclo[5.4.0]undeca-7-ene (DBU, 1.44 mol) was added. While themixture was cooled under stirring in an ice bath, 724 g ofperfluoro-1-octanesulfonylfluoride (1.44 mol) was added dropwise at aninternal temperature of 2 to 10° C. The mixture was stirred at aninternal temperature of 2 to 7° C. for 30 minutes. The mixture was thenallowed to warm to room temperature and stirred for 2 hours.Subsequently, the reaction mixture was allowed to stand and the toluenelayer (top layer) was collected. 1.83 L of toluene was added to thebottom layer and this mixture was stirred for 10 minutes. The resultingmixture was then allowed to stand and the toluene layer (top layer) wascollected. The toluene layers were combined and concentrated underreduced pressure. The resulting residue was subjected to silica gelcolumn chromatography [silica gel 60 (spherical, 63-210 μm), 3.66 kg,eluant=hexane:ethyl acetate=6:1->3:1]. The fraction containing thetarget product was collected and concentrated under reduced pressure togive 290 g of the title compound as a yellow oil (79% yield in the 2steps).

¹H-NMR (CDCl₃, 400 MHz) δ: 0.36-0.50 (4H, m), 1.77-1.83 (1H, m),2.38-2.54 (1H, m), 2.61-2.70 (1H, m), 2.85 (1H, dd, J=12.5, 6.8 Hz),3.06 (1H, dt, J=20.2, 8.5 Hz), 3.42-3.82 (5H, m), 4.92-5.17 (3H, m),7.21-7.37 (10H, m).

ESI-MS (positive): m/z 383 [M+H]⁺

Example 8 Synthesis of(3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidine

2.90 L of ethanol was added to 290 g of benzyl(3S,4S)-3-(N-benzyl-N-cyclopropyl)aminomethyl-4-fluoropyrrolidine-1-carboxylate(758 mmol) to dissolve the compound. The air in the reaction system wasreplaced by argon. 58.0 g of 10% palladium carbon was added and argonwas replaced by hydrogen. The mixture was then stirred at roomtemperature for 24.5 hours. Subsequently, hydrogen was replaced by argonand the catalyst was separated by filtration and washed with 290 mL ofethanol. The filtrate and the wash were combined and concentrated underreduced pressure to give 110 g of a crude product of the title compoundas a yellow oil. This product was used in the subsequent step withoutfurther purification.

Example 9 Synthesis of(3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidine dihydrochloride

360 mL of ethanol was added to 110 g of(3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidine (equivalent to 758mmol) to dissolve the compound. While this solution was stirred, 1.38 Lof a 10% hydrogen chloride-methanol solution was added dropwise at aninternal temperature of 27 to 33° C. 1.68 L of ethyl acetate was thenadded dropwise for crystallization (internal temperature of 19° C.). Themixture was stirred for 10 minutes at an internal temperature of 19° C.Subsequently, 1.08 L of ethyl acetate was added dropwise at an internaltemperature of 18 to 19° C. and the mixture was stirred for 30 minutesat an internal temperature of 18 to 19° C. The resulting crystals werecollected by filtration and washed with 600 mL of a 2:1 mixture of ethylacetate/methanol. The washed product was drained for 30 minutes anddried by air-blowing at 60° C. for 17 hours to give 82.7 g of a crudeproduct as reddish white powder crystals. To the crude product (82.5 g),0.83 L of ethanol was added and 50 mL of purified water was addeddropwise at an external temperature of 60 to 70° C. to dissolve theproduct (internal temperature of 65° C.). The solution was allowed tocool under stirring and then cooled in a water bath while kept stirredfor crystallization (internal temperature of 28.0° C.). The mixture wascontinuously cooled in a water bath under stirring until its internaltemperature was 20° C., after which it was cooled in an ice bath understirring for 1 hour. The crystallized product was collected byfiltration at an internal temperature of 3° C. and washed with 0.25 L ofethanol. The washed product was drained for 30 minutes and air-dried togive 48.2 g of the title compound as brown powder crystals (27% yield inthe 2 steps).

Melting point: 199.9-202.1° C.

¹H-NMR (DMSO-d₆, 400 MHz) δ: 0.72-0.80 (2H, m), 0.90-1.07 (2H, m),2.69-2.88 (2H, m), 3.02-3.16 (2H, m), 3.29-3.32 (2H, m), 3.41-3.64 (3H,m), 5.37-5.55 (1H, m), 9.63 (4H, br s).

CI-MS (positive): m/z 199 [M+H]⁺

[α]_(D) ²⁴-20.0 (c=0.30, distilled water)

Example 10 Synthesis of 1-benzyl 3-ethyl(3R,4S)-4-hydroxypyrrolidine-1,3-dicarboxylate

43 mL of anhydrous N,N-dimethylformamide was added to 1.15 g of benzeneruthenium (II) chloride dimer (2.30 mmol) and 3.00 g of (R)-(−)-BINAP(4.82 mmol) in a stream of argon gas. The mixture was stirred in an oilbath at an external temperature of 95 to 105° C. for 10 minutes. Themixture was then allowed to cool to room temperature. Volatile materialswere evaporated under reduced pressure (using a vacuum pump) in an oilbath at an external temperature of 50 to 70° C. to give a catalyst. 33.5g of 1-benzyl 3-ethyl 4-oxopyrrolidine-1,3-dicarboxylate (115 mmol) and68 mL of dehydrated dichloromethane were placed in an autoclave and theair in the autoclave was replaced by argon. The catalyst dissolved in100 mL of dehydrated dichloromethane was then added and the atmospherein the autoclave was replaced by hydrogen gas three times. The mixturewas stirred under a pressurized hydrogen atmosphere (8.83 MPa) at anexternal temperature of 50 to 60° C. for 4 hours. Heating/stirring wasstopped, and the mixture was left overnight. Subsequently, hydrogen gaswas released and the mixture was transferred to a different vessel andwashed with 30 mL of dehydrated dichloromethane. The mixture was thenconcentrated under reduced pressure and dried in vacuo at roomtemperature for 30 minutes to give 42.3 g of a crude product of thetitle compound as a dark brown oil. This product was used in thesubsequent step without further purification.

¹H-NMR (CDCl₃, 400 MHz) δ: 1.27 (3H, t, J=7.3 Hz), 2.37 (1H, brs),2.96-3.07 (1H, m), 3.33-3.40 (1H, m), 3.62-3.87 (3H, m), 4.19 (2H, q,J=7.3 Hz), 4.56-4.60 (1H, m), 5.14 (2H, s), 7.31-7.37 (5H, m).

EI-MS: m/z 293 (M)⁺

Example 11 Synthesis of(3R,4S)-1-benzyloxycarbonyl-4-hydroxypyrrolidine-3-carboxylic acid

42.1 g of 1-benzyl 3-ethyl(3R,4S)-4-hydroxypyrrolidine-1,3-dicarboxylate (equivalent to 114 mmol)was suspended in 330 mL of ethanol. To this suspension, 330 mL of waterwas added and the mixture was cooled in an ice bath. While the mixturewas stirred, 6.84 g of a solution of sodium hydroxide (171 mmol) in 330mL of water was added dropwise at an internal temperature of 5 to 10° C.and the mixture was stirred for 1 hour. Subsequently, 6.60 g ofactivated carbon was added and the mixture was stirred at roomtemperature for 30 minutes. The insoluble material was separated byfiltration through Celite and washed with 110 mL of water. The filtrateand the wash were combined and ethanol (approx. 330 mL) was evaporatedunder reduced pressure. The resulting residue was washed twice with 200mL of diisopropyl ether and the aqueous layer was filtered throughCelite. 30.0 mL of 6 mol/L hydrochloric acid was added to the filtrateand the mixture was stirred for 10 minutes. 300 mL of ethyl acetate and200 g of sodium chloride were added and the mixture was further stirredfor 30 minutes. The organic layer was collected and washed with 300 mLof 28% brine. To this layer, 30.1 g of anhydrous sodium sulfate wasadded and the mixture was stirred for 30 minutes. The mixture was thenfiltered through a cotton plug and washed with 50 mL of ethyl acetate.The filtrate and the wash were combined and concentrated under reducedpressure. The resulting residue was dried in vacuo at room temperaturefor 4 hours to give 26.5 g of a crude product of the title compound as adark brown amorphous material. This product was used in the subsequentstep without further purification.

¹H-NMR (CDCl₃, 400 MHz) δ: 2.98-3.08 (1H, m), 3.32-3.39 (1H, m),3.58-3.83 (3H, m), 4.55-4.59 (1H, m), 5.12 (2H, d, J=1.5 Hz), 7.27-7.35(5H, m).

EI-MS: m/z 265 (M)⁺

Example 12 Synthesis of benzyl(3R,4S)-3-(N-cyclopropyl)carbamoyl-4-hydroxypyrrolidine-1-carboxylate

17.9 g of 1-hydroxybenzotriazole hydrate (117 mmol), 16.9 mL ofcyclopropylamine (244 mmol) and 22.4 g of1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide hydrochloride (117 mmol)were successively added to a solution of(3R,4S)-1-benzyloxycarbonyl-4-hydroxypyrrolidine-3-carboxylic acid (25.9g, 97.5 mmol) in 259 mL of dehydrated tetrahydrofuran under stirring atroom temperature. The mixture was further stirred at room temperaturefor 5 hours. Subsequently, the reaction mixture was concentrated underreduced pressure, followed by addition of 130 mL of ethyl acetate and260 mL of 1 mol/L hydrochloric acid and subsequent stirring for 30minutes. The resulting crystals were collected by filtration and washedwith 26 mL of ethyl acetate. The organic layer was collected and washedwith 130 mL of a 10% aqueous sodium bicarbonate solution and 130 mL of28% brine. To this layer, 39.0 g of anhydrous sodium sulfate was addedand the mixture was stirred for 1 hour. The insoluble material wasseparated by filtration and washed with 52 mL of ethyl acetate. Thefiltrate was concentrated under reduced pressure. To the resultingresidue, 156 mL of diisopropyl ether was added and the product wastritulated. The precipitated powder was collected by filtration andwashed with 39 mL of diisopropyl ether. The washed product was dried byair-blowing at room temperature for 30 minutes. 25.6 g of the resultingcrystals were added to 308 mL of ethyl acetate. The mixture was heatedat an external temperature of 80° C. for 25 minutes under stirring, thenallowed to cool in the air for 40 minutes under stirring, then cooled ina water bath for 5 minutes under stirring at an internal temperature of40° C., and then stirred at room temperature for 5 minutes at aninternal temperature of 25° C. The precipitated powder was collected byfiltration and washed with 52 mL of diisopropyl ether. The washedproduct was dried for 1 hour by air-blowing. Further drying the productby air-blowing at 60° C. for 16 hours gave 14.5 g of the title compoundas fluffy colorless crystals (43% yield in the 3 steps).

Melting point: 132.0-133.4° C.

¹H-NMR (CDCl₃, 400 MHz) δ: 0.51 (2H, brs), 0.76-0.81 (2H, m), 2.70-2.79(3H, m), 3.26 (1H, dd, J=7.1, 11.0 Hz), 3.52-3.62 (1H, m), 3.72-3.90(2H, m), 4.46-4.51 (1H, m), 5.12 (2H, s), 6.04 (1H, d, J=16.1 Hz),7.30-7.36 (5H, m).

CI-MS (positive): m/z 305 [M+H]⁺

[α]_(D) ²⁴ −24.0 (c=0.40, methanol)

Optical purity: 99.9% ee

(HPLC Conditions)

Column=CHIRAL CELL AD-RH (4.6φ×150 mm), Daicel; precolumn=INERTSIL ODS-3(4.0φ×10 mm), GL sciences; detection wavelength=210 mm; flow rate=1.0mL/min; mobile phase=diluted phosphoric acid (1 to 1000 fold):acetonitrile=75:25; RT=8.33 min.

Example 13 Synthesis of benzyl(3R,4S)-3-cyclopropylaminomethyl-4-hydroxypyrrolidine-1-carboxylate

To a solution ofbenzyl(3R,4S)-3-(N-cyclopropyl)carbamoyl-4-hydroxypyrrolidine-1-carboxylate(14.5 g, 47.6 mmol) in 116 mL of dehydrated tetrahydrofuran, 122 mL of atetrahydrofuran solution of borane-tetrahydrofuran complex (1.17 mol/L,143 mmol) was added dropwise over 20 minutes at an internal temperatureof 40 to 44° C. The mixture was stirred at the same temperature for 7hours. Subsequently, the reaction mixture was cooled to an internaltemperature of 25° C. or below. At an internal temperature of 15 to 25°C., 14.5 mL of water was added dropwise and the mixture was stirred for20 minutes. At an internal temperature of 10 to 18° C., 39.8 mL oftriethylamine (286 mmol) was added dropwise and the mixture was stirredfor 5 minutes. The mixture was then refluxed for 15 hours. Subsequently,the mixture was allowed to cool and concentrated under reduced pressure.To the resulting residue, 44 mL of water was added and the mixture wasextracted with 102 mL of ethyl acetate. The organic layer was washedwith 73 mL of water and extracted with 60 mL of 2 mol/L hydrochloricacid. The aqueous layer was cooled in a water bath under stirring and 60mL of a 2 mol/L sodium hydroxide solution was added at an internaltemperature of 20 to 28° C. to adjust the pH to about 12. This mixturewas extracted with 102 mL of ethyl acetate. The organic layer was washedwith 73 mL of 28% brine. To the organic layer, 20.2 g of anhydroussodium sulfate was added and the mixture was stirred for 1 hour.Subsequently, the mixture was filtered through a cotton plug and washedwith 22 mL of ethyl acetate. The filtrate and the wash were combined andconcentrated under reduced pressure. The product was dried at roomtemperature under reduced pressure for 1 hour to give 14.3 g of a crudeproduct of the title compound as a pale yellow oil. This product wasused in the subsequent step without further purification. ¹H-NMR (CDCl₃,400 MHz) δ: 0.26-0.51 (4H, m), 2.09-2.19 (2H, m), 2.63-2.70 (1H, m),2.93-3.07 (2H, m), 3.17-3.25 (1H, m), 3.61-3.69 (1H, m), 3.74-3.81 (1H,m), 4.04-4.09 (1H, m), 5.12 (2H, d, J=2.0 Hz), 7.30-7.37 (5H, m).

CI-MS (positive): m/z 291 [M+H]⁺

Example 14 Synthesis of benzyl(3R,4S)-3-cyclopropylaminomethyl-4-hydroxypyrrolidine-1-carboxylatehydrochloride

42.0 mL of a 10% hydrogen chloride-methanol solution was added dropwiseto a solution ofbenzyl(3R,4S)-3-cyclopropylaminomethyl-4-hydroxypyrrolidine-1-carboxylate(13.9 g, equivalent to 46.4 mmol) in 195 mL of ethyl acetate understirring at room temperature (crystallization occurred during theaddition). Once crystallization took place, the mixture was stirred for15 minutes at an internal temperature of 20 to 22° C. Subsequently, 390mL of diisopropyl ether were added dropwise and the mixture was furtherstirred for 30 minutes. The resulting crystals were collected byfiltration and washed with 28 mL of diisopropyl ether. The washedproduct was dried for 30 minutes by air-blowing and further dried at 60°C. for 2 hours under reduced pressure to give 13.5 g of the titlecompound as a colorless crystalline powder (92% yield in the 2 steps).

¹H-NMR (DMSO-d₆, 400 MHz) δ: 0.73 (2H, brs), 0.86 (2H, brs), 2.38 (1H,brs), 2.67-2.73 (1H, m), 2.95-3.01 (1H, m), 3.08-3.26 (3H, m), 3.52-3.66(2H, m), 4.03-4.08 (1H, m), 5.07 (2H, d, J=2.9 Hz), 5.47 (1H, d, J=3.9Hz), 7.30-7.40 (5H, m), 8.97 (2H, brs).

[α]_(D) ²⁴ −34.1 (c=0.40, methanol)

Example 15 Synthesis of benzyl(3R,4S)-3-(N-benzyl-N-cyclopropyl)aminomethyl-4-hydroxypyrrolidine-1-carboxylate

40 mL of ethanol and 40 mL of water were added to 13.5 g ofbenzyl(3R,4S)-3-cyclopropylaminomethyl-4-hydroxypyrrolidine-1-carboxylatehydrochloride (41.2 mmol) to dissolve the compound. To this solution,7.62 g of sodium bicarbonate (90.7 mmol) and 8.46 g of benzyl bromide(49.5 mmol) were added and the mixture was stirred for 3 hours at aninternal temperature of 40 to 45° C. Subsequently, ethanol (approx. 40ml) was evaporated under reduced pressure and 65 mL of ethyl acetate wasadded to the resulting residue. This mixture was washed twice with 65 mLof 28% brine. The organic layer was dried over 15.0 g of anhydroussodium sulfate and concentrated under reduced pressure. The resultingresidue was subjected to silica gel column chromatography (silica gel60N (spherical, neutral) 400 g, hexane:ethyl acetate=2:1→1:1). Thefraction containing the target product was collected and concentratedunder reduced pressure to give 16.8 g of the title compound as acolorless amorphous material (quant.).

¹H-NMR (CDCl₃, 400 MHz) δ: 0.34-0.60 (4H, m), 1.77-1.84 (1H, m),2.31-2.45 (1H, m), 2.54-2.73 (2H, m), 2.89-2.95 (1H, m), 3.18 (1H, ddd,J=7.1, 10.7, 15.4 Hz), 3.26-3.37 (1H, m), 3.53-3.68 (3H, m), 3.84-3.91(2H, m), 5.10 (2H, d, J=2.4 Hz), 7.24-7.36 (10H, m).

ESI-MS (positive): m/z 381 [M+H]⁺

Example 16 Synthesis of benzyl(3R,4R)-3-(N-benzyl-N-cyclopropyl)aminomethyl-4-fluoropyrrolidine-1-carboxylate

9.16 mL of 1,8-diazabicyclo[5.4.0]undeca-7-ene (61.2 mmol) was added toa solution ofbenzyl(3R,4S)-3-(N-benzyl-N-cyclopropyl)aminomethyl-4-hydroxypyrrolidine-1-carboxylate(16.7 g, 40.8 mmol) in 167 mL of toluene. While this solution was cooledin an ice bath under stirring, 16.9 mL of perfluoro-1-octanesulfonylfluoride (61.2 mmol) was added dropwise and the mixture was stirred atan internal temperature of 3 to 5° C. for 1 hour. The top layer wascollected and the bottom layer was extracted twice with 50 mL oftoluene. The toluene layers were combined and concentrated under reducedpressure. The resulting residue was subjected to silica gel columnchromatography (silica gel 60N (spherical, neutral) 500 g, hexane:ethylacetate=4:1). The fraction containing the target product was collectedand concentrated under reduced pressure to give 12.7 g of the titlecompound as a pale yellow oil (82%).

¹H-NMR (CDCl₃, 400 MHz) δ: 0.36-0.50 (4H, m), 1.77-1.83 (1H, m),2.37-2.56 (1H, m), 2.60-2.70 (1H, m), 2.84 (1H, dd, J=7.1, 12.5 Hz),3.06 (1H, dt, J=10.9, 16.9 Hz), 3.50 (1H, ddt, J=3.8, 13.3, 40.1 Hz),3.59-3.82 (4H, m), 4.92-5.08 (1H, m), 5.09-5.17 (2H, m), 7.21-7.40 (10H,m).

ESI-MS (positive): m/z 383 [M+H]⁺

Example 17 Synthesis of(3S,4R)-3-cyclopropylaminomethyl-4-fluoropyrrolidine

1.25 g of 10% palladium carbon suspended in 25 mL of ethanol was addedto a solution ofbenzyl(3R,4R)-3-(N-benzyl-N-cyclopropyl)aminomethyl-4-fluoropyrrolidine-1-carboxylate(12.5 g, 32.7 mmol) in 100 mL of ethanol. The air in the reaction systemwas replaced by argon, which was then replaced by hydrogen gas. In thehydrogen atmosphere (atmospheric pressure), the reaction mixture wasstirred for 16 hours at an external temperature of 27° C. Subsequently,the atmosphere in the reaction system was replaced by argon and 1.41 gof 10% palladium carbon catalyst was added. The atmosphere in thereaction system was then replaced by hydrogen gas. In the hydrogenatmosphere (atmospheric pressure), the reaction mixture was stirred for3 hours at an external temperature of 30° C. Subsequently, theatmosphere in the reaction system was replaced by argon and the mixturewas filtered through cellulose powder, which was washed with 125 mL ofethanol. The filtrate and the wash were combined and concentrated underreduced pressure. Drying the concentrated product under reduced pressuregave 4.87 g of a crude product of the title compound as a pale yellowoil (94% yield).

¹H-NMR (CDCl₃, 400 MHz) δ: 0.30-0.47 (4H, m), 2.00 (2H, brs), 2.12-2.17(1H, m), 2.19-2.36 (1H, m), 2.76-2.82 (2H, m), 2.96-3.13 (3H, m), 3.24(1H, dd, J=13.7, 24.9 Hz), 5.10 (1H, dt, J=3.9, 54.7 Hz).

CI-MS (positive): m/z 159 [M+H]⁺

Example 18 Synthesis of(3S,4R)-3-cyclopropylaminomethyl-4-fluoropyrrolidine dihydrochloride

To a solution of (3S,4R)-3-cyclopropylaminomethyl-4-fluoropyrrolidine(4.74 g, 30.0 mmol) in 15 mL of methanol, 60.0 mL of a 10% hydrogenchloride-methanol solution was added dropwise over 10 minutes understirring at room temperature. The mixture was stirred for 5 minutes. 75mL of ethyl acetate was then added dropwise over 10 minutes and themixture was further stirred for 10 minutes. 50 mL of ethyl acetate wasfurther added dropwise over 10 minutes and the mixture was furtherstirred for 30 minutes. The resulting crystals were collected byfiltration and washed with 100 mL of ethyl acetate. The washed productwas dried at 50° C. under reduced pressure for 4 hours to give 4.98 g ofthe title compound as a faint brown crystalline powder (72% yield).

¹H-NMR (DMSO-d₆, 400 MHz) δ: 0.71-0.78 (2H, m), 0.88-0.99 (2H, m),2.67-2.88 (2H, m), 3.04 (1H, t, J=11.7 Hz), 3.14 (1H, dd, J=7.3, 13.2Hz), 3.30 (1H, dd, J=6.3, 13.2 Hz), 3.47-3.63 (3H, m), 5.47 (1H, dt,J=2.9, 52.7 Hz), 9.63 (4H, brs).

[α]_(D) ²⁴ 20.8 (c=1.00, purified water)

Example 19 Synthesis of benzyl(3S,4S)-3-(N-tert-benzyloxycarbonyl-N-cyclopropyl)aminomethyl-4-hydroxypyrrolidine-1-carboxylate

To a solution of 654 mg of benzyl(3R,4S)-3-cyclopropylaminomethyl-4-hydroxypyrrolidine-1-carboxylatehydrochloride (2.00 mmol) in 2 mL of ethanol and 2 mL of water, 504 mgof sodium bicarbonate (6.00 mmol) and 512 mg of benzyl chloroformate(3.00 mmol) were added and the mixture was stirred at room temperaturefor 8 hours. Subsequently, the reaction mixture was concentrated underreduced pressure and 20 mL of ethyl acetate was added to the resultingresidue. This mixture was washed with 20 mL water and then 20 mL of 28%brine. The organic layer was dried over anhydrous sodium sulfate andconcentrated under reduced pressure. The resulting residue was subjectedto silica gel column chromatography (silica gel 60N (spherical, neutral)50.2 g, hexane:ethyl acetate=1:2). The fraction containing the targetproduct was collected and concentrated under reduced pressure to give841 mg of the title compound as a colorless amorphous material (99%yield).

¹H-NMR (CDCl₃, 400 MHz) δ: 0.61-0.81 (4H, m), 2.32-2.39 (1H, m),2.59-2.66 (1H, m), 3.14-3.31 (3H, m), 3.38-3.48 (1H, m), 3.64-3.74 (2H,m), 4.10 (1H, brs), 5.09-5.19 (4H, m), 7.30-7.40 (10H, m).

ESI-MS (positive): m/z 425 [M+H]⁺

Example 20 Synthesis of benzyl(3S,4R)-3-(N-tert-benzyloxycarbonyl-N-cyclopropyl)aminomethyl-4-hydroxypyrrolidine-1-carboxylate

448 mg of 1,8-diazabicyclo[5.4.0]undeca-7-ene (2.94 mmol) and 1.48 g ofperfluoro-1-octanesulfonyl fluoride (2.94 mmol) were added dropwise to asolution ofbenzyl(3R,4S)-3-(N-tert-benzyloxycarbonyl-N-cyclopropyl)aminomethyl-4-hydroxypyrrolidine-1-carboxylate(832 mg, 1.96 mmol) in 10 mL of toluene under stirring in an ice bath.The mixture was stirred for 1 hour at an external temperature of 0 to10° C. Subsequently, the reaction mixture was concentrated under reducedpressure. The resulting residue was subjected to silica gel columnchromatography (silica gel 60N (spherical, neutral) 85.0 g, hexane:ethylacetate=2:1). The fraction containing the target product was collectedand concentrated under reduced pressure to give 266 mg of the titlecompound as a pale yellow viscous oil (32% yield).

¹H-NMR (CDCl₃, 400 MHz) δ: 0.63-0.71 (2H, m), 0.80-0.83 (2H, m),2.56-2.66 (2H, m), 3.21-3.31 (1H, m), 3.39-3.54 (2H, m), 3.57-3.62 (1H,m), 3.68-3.87 (2H, m), 4.99-5.18 (5H, m), 7.30-7.38 (10H, m).

ESI-MS (positive): m/z 427 [M+H]⁺

Example 21 Synthesis of benzyl(3S,4S)-3-(N-tert-butoxycarbonyl-N-cyclopropyl)aminomethyl-4-hydroxypyrrolidine-1-carboxylate

504 mg of sodium bicarbonate (6.00 mmol) and 655 mg of di-t-butyldicarbonate (3.00 mmol) were added to a solution ofbenzyl(3R,4S)-3-cyclopropylaminomethyl-4-hydroxypyrrolidine-1-carboxylatehydrochloride (654 mg, 2.00 mmol) in 2 mL of ethanol and 2 mL of water.The mixture was stirred at room temperature for 8 hours. Subsequently,the reaction mixture was concentrated under reduced pressure and 20 mLof ethyl acetate was added to the resulting residue. This mixture waswashed with 20 mL of water and 20 mL of 28% brine. The organic layer wasdried over anhydrous sodium sulfate and concentrated under reducedpressure. The resulting residue was subjected to silica gel columnchromatography (silica gel 60N (spherical, neutral) 51.1 g, hexane:ethylacetate=1:2). The fraction containing the target product was collectedand concentrated under reduced pressure to give 757 mg of the titlecompound as a colorless amorphous material (97% yield).

¹H-NMR (CDCl₃, 400 MHz) δ: 0.56-0.79 (4H, m), 1.46 (9H, d, J=4.4 Hz),2.27-2.34 (1H, m), 2.51-2.55 (1H, m), 3.15-3.41 (4H, m), 3.64-3.81 (2H,m), 4.08-4.12 (1H, m), 5.13 (2H, d, J=2.9 Hz), 7.29-7.38 (5H, m).

ESI-MS (positive): m/z 391 [M+H]⁺

Example 22 Synthesis of benzyl(3S,4R)-3-(N-tert-butoxycarbonyl-N-cyclopropyl)aminomethyl-4-fluoropyrrolidine-1-carboxylate

436 mg of 1,8-diazabicyclo[5.4.0]undeca-7-ene (2.87 mmol) and 1.44 g ofperfluoro-1-octanesulfonylfluoride (2.87 mmol) were added dropwise to asolution ofbenzyl(3R,4S)-3-(N-tert-butoxycarbonyl-N-cyclopropyl)aminomethyl-4-hydroxypyrrolidine-1-carboxylate(744 mg, 1.91 mmol) in 10 mL of toluene under stirring in an ice bath.The mixture was stirred for 1 hour at an external temperature of 1 to10° C. Subsequently, the reaction mixture was concentrated under reducedpressure and the resulting residue was subjected to silica gel columnchromatography (silica gel 60N (spherical, neutral) 80.1 g, hexane:ethyl acetate=2:1). The fraction containing the target product wascollected and concentrated under reduced pressure to give 99.5 mg of thetitle compound as a pale yellow viscous oil (13% yield).

¹H-NMR (CDCl₃, 400 MHz) δ: 0.61-0.62 (2H, m), 0.76-0.78 (2H, m), 1.46(9H, d, J=2.9 Hz), 2.49-2.64 (2H, m), 3.24-3.88 (6H, m), 5.01-5.18 (3H,m), 7.32-7.37 (5H, m).

ESI-MS (positive): m/z 393 [M+H]⁺

INDUSTRIAL APPLICABILITY

The present invention provides an industrially advantageous process forthe production of (3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidineor enantiomers thereof. According to the process of the presentinvention, the target compounds are produced via a novel productionintermediate(3R,4S)-1-protected-3-cyclopropylcarbamoyl-4-hydroxypyrrolidine orenantiomers thereof.

Enabling industrially advantageous production of(3R,4S)-3-cyclopropylaminomethyl-4-fluoropyrrolidine or enantiomersthereof, the process of the present invention realizes industriallyadvantageous production of10-(3-cyclopropylaminomethyl-4-fluoropyrrolidinyl)pyridobenzoxazinecarboxylic acid derivatives, novel antimicrobial agents that are notonly safe and potent, but are also effective against drug-resistantbacteria that can hardly be killed by conventional antimicrobial agents.Thus, high-quality pharmaceutical products using these antimicrobialagents can be provided by the present invention.

1. A method for producing an optically active3-cyclopropylaminomethyl-4-fluoropyrrolidine represented by thefollowing chemical formula (IX):

or an enantiomer thereof and/or a salt or a hydrate thereof, comprisingthe steps of: asymmetrically hydrogenating, with a transitional metalcatalyst, a 1-protected-4-oxo-3-pyrrolidine carboxylic acid esterderivative represented by the following general formula (I):

(wherein R₁ is a protecting group for amino group; and R₂ is a loweralkyl group) to obtain an optically active 4-hydroxy-3-pyrrolidinecarboxylic acid ester derivative of the following general formula (II):

(wherein R₁ and R₂ are as defined above) or an enantiomer thereof;hydrolyzing the ester group of the compound of the general formula (II)to obtain an optically active 4-hydroxy-3-pyrrolidine carboxylic acidrepresented by the following general formula (III):

(wherein R₁ is as defined above) or an enantiomer thereof; condensingthe compound of the general formula (III) with cyclopropylamine (IV):

to obtain an optically active N-cyclopropyl-4-hydroxy-3-pyrrolidinecarboxylic amide derivative represented by the following general formula(V):

(wherein R₁ is as defined above) or an enantiomer thereof; reducing theamide group of the compound of the general formula (V) to obtain anoptically active 4-hydroxy-3-cyclopropylamino pyrrolidine derivativerepresented by the following general formula (VI):

(wherein R₁ is as defined above) or an enantiomer thereof; protectingthe amino group of the compound of the general formula (VI) to obtain anoptically active 4-hydroxy-3-cyclopropylamino pyrrolidine derivativerepresented by the following general formula (VII):

(wherein R₁ is as defined above; and R₃ is also an protecting group foramino group and is the same definition as R₁) or an enantiomer thereof;fluorinating the hydroxyl group at 4th position of the compound, of thegeneral formula (VII) to obtain an optically active3-cyclopropylaminomethyl-4-fluoropyrrolidine derivative represented bythe following general formula (VIII):

(wherein R₁ and R₃ are as defined above) or an enantiomer thereof; andremoving the amino-protecting groups R₁ and R₃ of the compound of thegeneral formula (VIII) to obtain the desired compound.
 2. The method forproducing an optically active3-cyclopropylaminomethyl-4-fluoropyrrolidine or an enantiomer thereofand/or a salt or a hydrate thereof according to claim 1, wherein theamino-protecting groups that R₁ and R₃ represent are each an aralkylgroup, such as a benzyl group and a p-methoxybenzyl group, or analkoxycarbonyl group, such as a methoxycarbonyl group, an ethoxycarbonylgroup, a propyloxycarbonyl group, an isopropyloxycarbonyl group, abutyloxycarbonyl group, an isobutyloxycarbonyl group, atert-butyloxycarbonyl group and an benzyloxycarbonyl group.
 3. AnN-cyclopropyl-4-hydroxy-3-pyrrolidine carboxamide derivative representedby the following general formula (V):

(wherein R₁ is an amino-protecting group), or an enantiomer thereof. 4.The N-cyclopropyl-4-hydroxy-3-pyrrolidine carboxamide derivative, or anenantiomer thereof according to claim 3, wherein the amino-protectinggroup that R₁ represent is an aralkyl group, such as a benzyl group anda p-methoxybenzyl group, or an alkoxycarbonyl group, such as amethoxycarbonyl group, an ethoxycarbonyl group, a propyloxycarbonylgroup, an isopropyloxycarbonyl group, a butyloxycarbonyl group, anisobutyloxycarbonyl group, a tert-butyloxycarbonyl group and anbenzyloxycarbonyl group.
 5. The N-cyclopropyl-4-hydroxy-3-pyrrolidinecarboxamide derivative, or an enantiomer thereof according to claim 3,wherein the compound of the general formula (V) is(3R,4S)-3-(N-cyclopropyl)carbamoyl-4-hydroxypyrrolidine-1-carboxylicacid benzyl ester,(3S,4R)-3-(N-cyclopropyl)carbamoyl-4-hydroxypyrrolidine-1-carboxylicacid benzyl ester,(3R,4S)-3-(N-cyclopropyl)carbamoyl-4-hydroxypyrrolidine-1-carboxylicacid tert-butyl ester,(3S,4R)-3-(N-cyclopropyl)carbamoyl-4-hydroxypyrrolidine-1-carboxylicacid tert-butyl ester,(3R,4S)-1-benzyl-N-cyclopropyl-4-hydroxy-3-pyrrolidine carboxamide or(3S,4R)-1-benzyl-N-cyclopropyl-4-hydroxy-3-pyrrolidine carboxamide.